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NMR structure of the BeF3-activated structure of the response regulator Chey2-Mg2+ from Sinorhizobium meliloti

Overview

The chemotactic signalling chain to the flagellar motor of Sinorhizobium, meliloti features a new type of response regulator, CheY2. CheY2 activated, by phosphorylation (CheY2-P) controls the rotary speed of the flagellar, motor (instead of reversing the sense of rotation), and it is efficiently, dephosphorylated by phospho-retrotransfer to the cognate kinase, CheA., Here, we report the NMR solution structures of the Mg(2+)-complex of, inactive CheY2, and of activated CheY2-BeF(3), a stable analogue of, CheY2-P, to an overall root mean square deviation of 0.042 nm and 0.027, nm, respectively. The 14 kDa CheY2 protein exhibits a characteristic open, (alpha/beta)(5) conformation. Modification of CheY2 by BeF(3)(-) leads to, large conformational changes of the protein, which are in the limits of, error identical with those observed by phosphorylation of the, active-centre residue Asp58. In BeF(3)-activated CheY2, the position of, Thr88-OH favours the formation of a hydrogen bond with the active site, Asp58-BeF(3), similar to BeF(3)-activated CheY from Escherichia coli. In, contrast to E.coli, this reorientation is not involved in a, Tyr-Thr-coupling mechanism, that propagates the signal from the incoming, phosphoryl group to the C-terminally located FliM-binding surface. Rather, a rearrangement of the Phe59 side-chain to interact with Ile86-Leu95-Val96, along with a displacement of alpha4 towards beta5 is stabilised in, S.meliloti. The resulting, activation-induced, compact alpha4-beta5-alpha5, surface forms a unique binding domain suited for specific interaction with, and signalling to a rotary motor that requires a gradual speed control. We, propose that these new features of response regulator activation, compared, to other two-component systems, are the key for the observed unique, phosphorylation, dephosphorylation and motor control mechanisms in, S.meliloti.

About this Structure

1P6U is a Single protein structure of sequence from Sinorhizobium meliloti. Full crystallographic information is available from OCA.

Reference

Solution structures of the inactive and BeF3-activated response regulator CheY2., Riepl H, Scharf B, Schmitt R, Kalbitzer HR, Maurer T, J Mol Biol. 2004 Apr 23;338(2):287-97. PMID:15066432

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